See Figures 1 and 2
The air bag system used on Volvo vehicles is referred to as Supplemental Restraint System (SRS). The SRS system provides additional protection for the driver, if a forward collision of sufficient force is encountered. The SRS assists the normal seat belt restraining system by deploying an air bag, via the steering wheel and, on some models, the passenger side of the dashboard.
The system also includes a knee bolster at the lower steering column area. It is used to absorb energy and control the driver's forward movement during an accident by limiting leg movement.
The system also includes a battery voltage check. The SRS warning lamp will illuminate, if the voltage falls below 9 volts. When the voltage rises above 9 volts again, the lamp will be go out after approximately 10 seconds.
The SRS system is monitored continuously by a microprocessor in the crash sensor. Any fault which is detected is stored in the memory and the SRS warning lamp will turn ON.
Some later Volvo models are equipped with a Side Impact Protection System (SIPS). Vehicles equipped with SIPS will contain a decal possibly located on the front windshield, drivers side of the instrument panel, below the seat pocket, or on the drivers side B-pillar.
The object of the SIPS system is to protect the occupants in the event of certain side-impact accidents. An air bag is deployed to cushion the impact against the outer side of the vehicle. This system uses sensor mounted in the seat bottom, just outside the seat track. If an accident occurs, the bag could deploy, triggered based upon information gathered by the crash sensor measuring the violence of the collision. This sophisticated process occurs in milliseconds.
The SIPS system is not part of the SRS system and has its own function, in fact unlike the SRS system, the SIPS system can deploy one side without deploying the other, depending on which side the impact occurs.
Under normal conditions, the SRS warning lamp will come ON when the ignition switch is turned to the ON position. If the engine is not started, the lamp will be extinguished after approximately 10 seconds. Failure of the warning lamp to go OFF, while driving, indicates a fault in the SRS system. The warning lamp will remain lit until the fault is corrected and the memory cleared.
The crash sensor records a combination of G-force and prolong deceleration. When a sufficiently high G-force and prolong deceleration are simultaneously recorded, the power unit will deliver a current which will trigger the gas generator of the inflatable bag. The bag will be filled in a few hundredths of a second with non-toxic nitrogen. Immediately after the collision, the gas is released through a ventilation hole and the air bag slowly collapses. The entire sequence of inflation and collapse takes approximately 0.2 milliseconds.
The SIPS system works very similar to the SRS, however the SIPS is completely mechanical. Only three components per side of the vehicle are used. The crash sensor operates very similar to the SRS and activates when an impact of the deformed door hits the sensor at a speed greater than 2 milliseconds or 6.6 ft. per second. No electricity is used, the crash sensor deploys an igniter that uses a charge very similar to the way a shotgun is fired to fill the bag.
The SIPS bag deploys and breaks through the seat cushion SIPS module cover. A stitch seam in the seat is strategically placed to aid in this process. The bag deploys toward the door to help protect the driver/passengers rib cage during a side-impact collision. There is a vent on the underside of the bag which will allow the bag to deflate slowly, acting as a brake on the driver/passenger.
Since the Supplemental Restraint System (SRS) is such a complex and critical safety system (which requires special precautions when repairs are being made), Volvo recommends that all repairs to the SRS system be performed by Volvo SRS-trained technicians.
DISARMING THE SYSTEM
- Turn the ignition switch to the OFF position.
- Disconnect the negative battery cable AND TAPE the cable end away from the battery.
ARMING THE SYSTEM
Assuming that the system components (air bag control module, sensors, air bag, etc.) are installed correctly and are in good working order, the system is armed whenever the batterys positive and negative battery cables are connected.